Feed-water heater



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` FEEDWATER HEATER Filed Dec. 1, 1922 14 sheetssheet 9 Fig. 25- 247 .23]'[46" ,144 133 Feb. 4, 1930. E. H. BLUNT FEEDWATER HEATER Filed Dec. l,1922 14 Sheets-Sheet 1l NVENroR Feb 4, 193D'. E.' H. BLUNT v FEEDWATERHEATER Filed Dec. f. 1922 14 sheets-sheet 12 lllllIIIIIIIIIIIIIIIIMINVENTOR Feb. 4 1930.. E. H. BLUNT v FEEDWATER HEATER Fired Dec. l. 192214 Sheets-Sheet l5 vENToR Hlunt,

Feb.v4, 1930. E. H. Bl- UNT FEEDWATER HEATER Filed Deo. 1. 1922 14Sheets-sheet 14 Patented Feb. 4, 1930 PATENT ortica nnnunn n. BLUNT, orNEW Yoan, N. Y.

FEED-WATER HEATER Application sied member 1, 1922. serial No. 604,414.

My invention relates particularly to apparatus for heating feedwater forlocomotive boilers and -has particular reference to what is commonlytermed the open type heater. In such constructions the cold feedwater islsprayed 4into a chamber which receives eX- haust steam. The steam isthus condensed and the waterhe'ated in thischamber. The heated:teedwater is withdrawn from this chamber and forced into the boilerbymeans of pump action. My former application #448,778,vi1ed March 1,1921, which has inatured intoPatent- 1,551,727, shows one form ofapparatus of this type. My present inven- .V tion contemplatesimprovements on thecon 4struction' etc. of my former application.

-v One object of my present invention is to construct apparatus havingmaterially great-v `.er capacity and at thel Sametime keep the i partscompact and yet accessiblewithin the limits imposed bycurrentilocomotive design. Another object is to insure uniformity ofaction under varying conditions of operation. y.Another object is tomake the apparatus comf pact and susceptible of standardization togeneral locomotive design.

I have specifically sought to automatically govern the pump action inaccordance with the quantity' of exhaust steamavailable for .L0 heatingpurposes. Another object is to regulate the speed of thepump undervarying conditions of demand. Another object is toso control the pumpaction as to. avoid4 excessive strains. Y

i Another object is to regulate the steam su plied to the opposite sidesof the pistons 1n accordancewith the work necessary to be done. Anotherobjectl is to normally permit the exhaust from the said pump to escapefor instance to the stack, but to utilize this exhaust in the 'heaterlwhen the normal heater supply is deficient. Another object is to takey, some of the excess steam vfrom the heater in and condense the steam.l Another object is to reduce the condensation in the heater when thewater level reaches a predetermined height. i

l .;Anothcr object is. to cushion the pump .ac-

tinfand thus obtain a maximum pumping i 45 such a manner as to utilizethe heat from it' capacity with a minimum length of cylinder. Anotherobject is to stop or slow down the pump automatically when the Waterlevel in the heater reaches an extreme low mark. Anotherv object is toautomatically return to the heater or to the heater side of the pumpsome of the hot water when the water level falls below a predeterminedoint. Another object is to regulate the spec of the pump in some directratio to the pressure of the exhaust steam in the heater tank. Anotherobject is to allow an excess of cold water at certain times to pass fromone pump to the other so as to prevent flooding the heater. Anotherobject is to pass some of the hot water from onepump to the other atcertain times so as to prevent abnormal lowering of the water level inthe heater tank. In a single unit apparatus the hot water would bepassedback to the heater or the heater side of the valve. Another objectis to approximately synchro- CII nize the action of the two water pumps;An-

other object'is to control the time of a pump cycle by varying theresistance tothe disc arge of water into the heater. Another object isto avoid trapping or pocketing air in the upper part of the pumpcylinder and passages. Another object is to vary the amount of hot-waterow to the pum in some direct ratio to the steam pressure in t e heatervessel. Another object is to use part ofthe high pressure exhaust of thepump, so as to operate the return stroke; for instance coinpounding.Another object is to provide the longest time for the spray to remain inthe vapor space, by spraying upward and deflecting laterally tocollecting trays.. Another object is to place the Water valves as nearlas possible in the direct line of ow, an so eliminate unnecessarychanges of direction," for instance; all the cold inlet valves areplaced between the source of supply and the points of delivery, that is,grouped about the right hand pump and near the top. Another object-,isto providel a maximum length of 95 pump stroke in, a given space.Another ob- Lect'is to obtain a maximum static hot water ead on thesuction valves or a given condition. Another object is to adapt theheater tank .to variations of locomotive boilerv de- 10 signs. Anotherobject is to permit convenient testing of the water valveswliile understatic water ressure. Another object is to construct t e apparatus sothat it can be suspended at a low level and take advantage oi a maximumhead on cold water suction valves. Another object is to facilitate theremoval and repacking of the piston rod stuffing box units withoutremoving the rods. Another object is to permit the employment of a pi:-

- ton rod sleeve in ysome cases without subjecting the sleeve toysubstantial compression. Another object is to purity the water byproviding ltering material which can be readily replaced withoutinterfering with the operation of the apparatus. Another object is toprovide means for satisfactorily indicating or registering the speed ofthe pump. l

Other details of the invention will be understood from the followingspecification,

in which I have described not only the preferi'ed construction but somemodifications and alternative combinations.

In one form of apparatus as herein shown land described,'I employ twopump cylinders andvfpistons, each of 'which is single acting on bothends as set nfort-h in my former application, that is, each iston drawscold feed-water into the cylin er on one side of the piston'at the sainetime that it is forcing to theboil'er. On the next'stroke-of the piston,the cold water is forced into the heater and het water is withdrawnlfrom; the heater into the opposite end ofthe cylinder. These two waterpistons are connected to steam pisi tons and start moving simultaneouslyin opposite directions. The steam pistons are controlled by ,a mainsteam valve and two aiixiliary reversing valves. These auxiliary valvesare controlled by the movement of thepistons so as to reverse the actionof the main valve when the two pistons have reached theends of their'strokes respectively.

vInasinufch as the feedwater requires only a comparatively smallpressure to force it into the heater and a relatively large pressure toforce it into ,the'boilen I provide means for applying correspondinglydifferent pressureson the opposite sides of 'each steamv piston.v Thismay be accomplished.` by a rey ',ducing valve of special design as shownin one form of the invention, or byI-nieans o f a compounding`arrangement as Vshown in anotherform vwhich has other advantages.

In View of the very small space available l onthe locomotive forapparatus of this kind, l

- I have designedtlie parts as compactly as possible fand yet so aste:facilitate assembling, testing, ad]ustment,.and repair.

, 5I have also endeavored to construct the pumpparts so as to check themovable parts gradually and avoid shock..

I. 0n account of the variations which loccur in the conditions and thewidely varying temperatures in which the apparatus must be capable ofoperating with a minimum of attention and adjustment, I have sought toautomatically take care of an excess amount of eed'water by means of a`circulating system,

so that the excess of cold feed-water from.

one pump is passed back to the other pump,

and an excess of hot water from oiie pump can be passed around to theother pump, or around'the .valves and back to the heater.

When a locomotive is in operation on the road, it is frequently called uon to drift or run without any apprecia'le amount` of steam being used.As a consequence, -there is but little exhaust steam. Most forms offeedwater heaters. require that under such circumstances the feedpump belslowed down or stopped by hand to prevent the puiping of cold waterinto the boiler; said pump being started up again when the locomotive isagain using steam. I Such requirement, however, demands altogether toomuch attention from the engineer, while, if neglected, it results inimproper operation. I propose to control the speed of the pumpsautomatically; for instance, by means of changes in presf sure oftheexhaust steam in the heater.

Figure 1 is a side view showing one. form of locomotive with feedwaterheating apparatus embodying improvements of my invention. i

Fig. 2is a plan view showing parts of the same.

Fig. 3 is 'an end view of the same.

Fig. 4 is an outside view of the principal novel parts of the apparatusvshown in Figs. 1 and 2. l

' Fig. 5 is a top'plan view of the same.

Fig. 6 is a front view of the same apparatus. V. f

Fig. 6EL is a fragmentary plan and section on line (SL-6" of Fig. 6.

v Fig. 7 is a rearview of the right hand pump. y

Fig. 7a is a vertical longitudinal-section of the main steam valve.

Fig. 8 is a plan view ofthe pumpv showing the piston rods in sectiononthe line 8-8,

Fig. 4. ig. 9 is a sectional view of the pump on the plane of the line9-9iof Fi 4.

F1 10 is a sectional view of t e pump on `the p ane of the line 10-10 ofFig. 4.

' Fig.r 11 a sectional view of the pump on the plane of the line 11`l1of Fig. 4.

Fig. 12 is a sectional view of the pump on l the plane of the line 12`12of Fig. 4.

v Fig. 13` is a vertical sectional view of the ump part ofthe apparatus,parts being roken away and foreshortened, the section being takensubstantially on the plane of the axes of the pistons. o y

Fig. 1,3l is afront end view of the-main steam valve casing.

Fig. 14 is a plan view of the upper or steam end of the pump, partsbeingbroken away or omitted, and otherpartsA being showngin 'm Fig. 17 is across section taken Fig. 16 isa front view andv section of the partsshown in Fig. 15.

generally on the line 17-17 of Fig. 16.

Fig. 18-` is 'a cross section on the broken plane of the' line 18-18 ofFig. 15.

lso

Figs. .1,9- to' 41 inclusive are more or lessy versing valve mechanismshown in the various positions which they occupy at differenttilnes;

Fig. 19-is a longitudinal vertical'sectional which they wouldoccupy whenthe righthand. piston is fully raisedand the left=hand piston isfully-depressed. It should be understood, however, that these valvesremain in these positions during the time that the respective pistonsare completing the inter.- mediate succee'ding strokes. This positionfor .convenience will .be termed the first position. v l f Fig. 2O is avertical sectional view on the plane of the line 20--20 of Fig. 19.

Fig. 21 is a similar section'on theplane ofV theline 21--21. v

Fig. 22 is a plan view of the stationary or fixed valve seat andconnecting passages, with the overlying valves removed, the flow inindicated by arrows.'

Fig. 22l is a sectional plan of the reversing valves rtaken slightlyabove the under surfaces and showing sections of ports and pas-Y -sa es.i y i 23shows the reversing valves in what maye. termed the secondposition, where the left-hand piston has reached the top of its vstrokeand thrown its valve, and the right- .hand piston is still descending.Fig. 24 is a section on the plane ofthe'line Fig. 25 is a sectionon theplane of the line of exhaust steamfor the iii-st positionl he- Fig. 26isl a vplan view of the stationary valve-seatl `and the registering.connections for the second position.

lan of the-stationary valve Eea-.and Siee-*Pwgsnd 'indicates fhjdiagra-mlnatic sections and detailsof the resy view of the reversingvvalves in the position.

Fig. 27 is alongitndinal, vertical, sectional plane of the une Fig. 32is a section on the plane of the line 32-32 of Fig. 29.

Fig. 33 is a plan of the stationary valveseat with passages, arrowsindicating flow of Ylive steam for the fourth position.

Fig. 34 is a longitudinal, vertical, sectional view of the reversingvalves in what may he termed the fifth position, where the right-handpiston has reached the top of'its stroke and the left-hand piston is'still Afalling. f I

Fig. 35 is a section on the plane of the line 35--35 of Fig. 34.

Fig. 36 is a section on A the plane of the line afs-36 of Fig. 34.

F ig. 37 is a planl of the stationary valveseat with arrows indicatingthe low of live steam when in the lifth position.

Fig. 38 is a longitudinal, vertical, sectional view with the parts inwhat may be termed the sixth position, where the lefthand. piston hasreached the lower end of itsstroke and the right-hand piston is still-yrismg;

Fig. 39 is a sectional view on the plane of the line 39-439 of Fig. 38.'

Fig. 40 isa sectional view on the plane of the line 40'-40 of Fig. 38. iFig. 41 indicates the live steam passages with the valves in theposition of Fig. 38.

Fig. 42 is a vertical sectional view 'of lefthand pump, also avfiltering device and a low water lloat control.

Fig. 43|is a vertical sectional view on the line 43-43 of Fig. 44showing ther detachrable filtering device.-

Fig. 44 is a horiaontal section on line 44-44 of Fig. 43.

Fig. .4`5is a vertical sectional view of thev upper or cold water end ofthe right-hand pump on the irregular section line l5-4 5 .of Fig. 9 butwith piston rod sleeve removed.

Fig. 4 6 is a vertical section of the-cold water dlscharge valve .onsectionof line f fic- 4e of Fig. 8.

Fig. 47 is a vertical sectional view of testing plug Fig.`48 is asection at right angles thereto.

Fig. 49 isa .side view and partial sectionof a single unit apparatuswith a steam ,valve and passages, and a spray control mechanism showninthe hi h-speed or o en position.

Fig.y 59 'is a ront sectiona view looking les ne i

liti

towards the locomotive cab, of a single unit.

apparatus, on the line --50 of Fig 51 with details for controlling theWaterv spray.

Fig. 51 is a plan view of pump and a partial section of the. heatervessel of Fig. 49.

Fig. 52 is a plan view and partial section at top of pump on the planeof the line .fa-52 of Fig.v 49.

Fig. 53 is a sectlonal view sliowing'part` of the spray. and pumpcontrol similar to that shown in Fig. 49 but'on the slow-speed orclosedposition, when-the heater pressure falls below a predetermined value.

Fig. 54 isa sectional view of an emergency low water control mechanism,on the line .54-54 of Fig. 5.

Fig. 5 on the line 59-59.

Fig. is a sectional detail ofthe compounding valve in the high positionwith all `,pipes and ports shown in a single vertical plane.- A

Fig. 61' is av sectional detail of the compounding valve in the lowposition. Fig. 62 is a side elevation and part section of a twin unitsteam cylinder with the main steam valve in the right hand position,when used for compounding.

Fig. 63 is a top plan of Fig. 62 with a reservoir tank and requiredpiping.

Fig. 64'is an end elevation and section of Fig. 62 on the line 64--6/i;`

Fig. 65 is a `plan'otf ports' and passages under the main valve andshowing the iiow of steam when the valve is in the left hand position;taken on the line (i5-65 ofFig. 62.

Figures 1, Zand' 3 of the drawings show i the invention in one form asapplied toa certain type'of locomotive. It should be understood, ofcourse, that this is merely .illustrative of one particular use of theinvention 1 showinga typical installation and suggest are designe inythe manifold .complicated 'problems invo ved in auch a construction.The cold water sup' ly is usually from 'a tanksuch a s 1 carrie yby atender.- VThe boiler-which ls to be fadv is` indicated at 2.-` Theexhaust steamwhich is used to rheat the. feedwater comes from theexhaust assages 3 and conduit'. Substantiall all t e parts of the'apparatus to be accommodatedfbelow what is commonly vtermed thevrunningboard 4 along "the sidev of the locomotive, the `board beingbroken away in Fig. 2 to showthe heat'- er' and adjacent air compressor.The heater tank 5 having an inspection door 5, is connected totheexhaust conduit 3 by pipe line 6 containing a stop check-valve 7andpreferably an oil 'separator 8.` Live steam for the n pump 9 owsthrough pipe 10, while exhaust vsteam is carried away byv pipe 10a,having ya check' valve 19a and a branch 17a (with included check valve)connected to theheater vessel. Cold water goes to the pump through pipe11 and hot water goes. tothe boiler through pipe 12. 1

Thel heater vis preferably made of three parts forstruct'ural reasons.'The back part 13 iitsin under the side of the boiler, and the extension14 provides additional vapor s ace and aiiords a connection for' the endo the exhaust pipe line 6,.as well asa housing for part of theVregulating mechanism. With a standardized main sectionof tank 5, theback I part 13, can be modified to i'it various shapes of exhaust steammay be supplied, forinstan'Ce, from the air compressor 15. In this casethe air compressor vshown is what is commonly known as across compoundair pump, although the type is immaterial to my invention. The auxiliaryexhaust steam pipe 1 6 is connected to the :heater by .a branch 17containing acheck valve 18 preferably at or close .to the heater. rlhepipe 16 may falso have a check valve 19 Alocated between the branch 17and thestack. :These valves are so adjusted that when. the pressure inthe heater is slightly less than that in the auxiliary exhaust linetothestack, the steam will pass yinto the heater while at'other times itgoesto the stack. The T 18IL in branch iping 17 ,A 1sl provided` with a plugfor a possi le exhaust connection from other auxiliaries;

Y. rThe cold water :from the tank 1 is drawn through the pipe 11 bymeans of pump 9 and forced through' pipe 20 intothe heater. This pumpmay be a single cylinder or twin cylinder depending upon-'the Ispaceavailable and the capacity'. required. In the preferred form,.l have'shwntl'le pump las having two pistons 2 1 and 22.-'ar`ranged.in'suitable cylinders and adapted 'to be operated by steam pressure. aswillk hereinafter be described. Each piston may be said to be singleacting so far asthe cold water is concernedvand single acting withlrespect tothe hot water. Thev cold water inlet valve-chamber is. divided into two separated parts 23 and 24, each of which preferablycontains a plurality of inlet valves 25 and 26,l adapted to be lifted asthe water vflows intoeach chamber from piston 21 is depressed, Water isdrawn in` through the valve chamber 23 and fills the space 28 above thepiston. When the piston p 21 rises the valve 25 is seated and the wateris forced through a valve 34 preferably of the multiple beat type, andthrough a pipe 35 to the pipe 20, and thence into the heater. In asimilar manner, when the piston 22 is depressed, water llows into thecylinder lspace 31 above the piston through the valve chamber 24 andconduit 29. When the piston 22 rises, the valve 26 is seated andthewater is forced through the discharge valve 36 to pipe 37 to pipe 20and thence into the heater. For convenience inconstruction andaccessibility, the chambers 23 and 24 are provided with covers 38 and 39held in place by bolts such-as 40 on the outer rim and set bolts 41 onthe inner rims.

To avoid shock atthe upper end of the piston stroke I may provide eachpiston with a flange 42 and introduce a supplemental stationary flange43 in the upper end of the cylinder, causing a restricted passage 44 to.form when the llange-42 reaches the end of its upstroke (Fig. 13). Asthe water must escape through the channel 33, it is clear that any waterwhich is trapped between the main part of the piston and the stullingbox-45 when' the flange 42 -lits over the stationary flange 43 can onlyescapeby leakage. I proy videpassages 46 of limited area for this reandt which the resistance may be regulated e speed near the endof thestroke correspondingly controlled. .j

The member 29 which carries the valve 36 is preferably a casting madeseparate from the lief bly;y

cylinders for convenience in construction and assembly. The valve 34 isalso preferably mounted in a separately formed casting.

- As a part of the regulating system I prefer to provide a spray Ahead50 through which the cold water is discharged into the heating chamber.This head is preferably supplied with V.a series of spray openings to bedescribed later on.

Above the spray head 50 I prefer to locate the deflecting or sprayingvmember 51 (see Fig. 6) against which the water from the the heating eectof the steam. TheA normalr water level in the heater is below the sprayhead and the capacity of the heater is suilicient to insure propersupply of water to the hot water'pump.

For convenience in construction, assembly, etc., the rear part 13 of theheater vessel preferably extends down below the rear of the main part 5providing a trap or settling chamber in which I may introduce ay bailleplate 53 extending below the inlet of the discharge pipe 54. Thisballle'tends to prevent .floating material from passing out to the ump.

The bottom of the pump is formed by a casting 55 which is connected tothe lower ends of the pump cylinders and to the discharge pipe 54. Testplugs 55 of special design are inserted below each water valve as willbe described later on.

Member 55 is provided with a horizontal valve deck 56 and a vertical webor partition 57 above the deck dividing it into a single lower chamberand two upper chambers both of which are provided with one or more hotwater inlet valves 58 and 59. 56 is a passage with plug to drain the hotwater pump. The valves 58 and 59 are arranged directly beneatli therespective pistons so that they con member 55 may bebolted or otherwisesuitably secured to the lower end of the pump cylmders and constitutes avery convenient method olil mounting the valves in such a way that theycan be readily removed, inspected and replaced. Y I

In order to save as much space as possible I prefer to form theattaching flange 60 on an incline and curve the lower end of thedischarge pipe 54 as indicated in Figs. 4 and f 6. It should be notedthat the upper end of the discharge pipe 54 extends backward to the part13 of the heater vessel. This construction permits a convenientinstallation and occupies a minimum of space.

Above the hot water inlet valves the pump .cylinders are provided withlateral extensions61, 62, 63 and 64 with water passages leading to theoutlet valves 65 and 66. Cover plates such as 67 and 68 permitconvenient access to the valves. The hot water drawn from the heaterflows by gravity into the chamber below the valve deck 56 then past thevalves 58 and 59 alternately and follows the pistons into theirrespective chambers when the pistons move upwardly. On the down strokeof the right hand piston 21 the hot water beneath it is forced upwardlypast the valves 65 into a common chamber 69 above allvoutlet valves andto the top of which are fastened the covers 67 and 68. The outlet 70from the chamber 69 delivers the hot water to pipe 71. This pipe 71 isconnected to a fitting 72 which in'turn is connected with pipe 12 whichleads to the boiler check-valve. To the fitting 72 I connect anair'reservoir 73 which is located alongside of the heaterv vessel .andbeneath the extension 14. When the 'left hand piston 22 is depressedthe, hot waterlbeneath it is forced past the valves 66 and into thechamber 69, outlet 70 and thence to the boiler.

In order `to cushion the downward stroke of eachl piston I may extendthe pump lining 74 downwardly and provide it with one Y or more openingsor a series of 'openings 74"u leading to the Iateralf passages 61 to 641nclusive. As the left-hand piston comes down,

its lower flange gradually covers its openings 74' and this-increasinglyrestricts the total area of the discharge outlet. This piston flange 75may be provided with one or more openings 76 to allow for the escape ofair' to opening 743. By recessing the casting94 (FiGs, 13 and 42) Iprovide space for the stung' box 45 and at the same time avoid airpockets at the upper end of the pump cylinder, as it is lower than thetop of the outlet 30, and cushioning means are estab- 2a lished wheneverthere is a conjunction between the stuiling'box and theA piston on theup stroke. The ,lower flange 75 not only provides cushioning means onthe down stroke ut also makes a recess for the nut on the,

lower end of the piston rod. e

It should be noted that by this system the pump handles a certain amountof cold water on the upper side of each piston and on the lower hotwater side is obliged to handle $5 not only the same quantity of waterbut also the condensed steam which has provided the heating medium, ifthe water level is to be maintained. I have located the power or steamcylinders 80 and 81 (Fig. 13) above the pump cylinders and connected thesteam pistons 82 and 83 to the pump pistons 21 and 22 respectively bymeans of piston rods 84 and 85. Each piston rod is preferably threadedinto its steam piston and bolted to the pump piston as shown in Figure13. As a result of this general construction which is more fullydescribed and claimed in my former application above referred to, theeffective area ofthe lower, or hot water, face of each pump piston ismaterially greater than the cold Water area, this excess being v equaltothe cross sectional area of the piston rod. Qbviously the excessvolume of water which can be handled by the hot waterk n orderpreferably loose fitting has several internal` ianges 87 that act asguides for the inner rod and prevent lateral deflection. To prevent thesleeve 86 from carrying an excessive thrust andffor which it is notdesigned, I

provide yielding material such as at 88 for one or both ends, orotherwise pack Vto prevent leakage into the space between the piston rodand sleeve. 1

To accommodate the pistonl rod and various sized sleeves, I providestutiing boxes 89 with a screw cap 90, having an inner Harige 93 adaptedto bear on a split gland 91 whose parts are doweled or otherwise securedto-l gether,vand which can be removed and replaced with larger.orsmallerglands toaccommodate various sizes of piston rods or sleeves.

Figia 45 shows 'an adaptation lof the `sam stuliing box and screw cup tothe piston rod 84, when the sleeve 86 is removed. 86a isa dotted outlineof the maximum diameter sleeve for which the stufiing box is designed,while 91a is a modified form of split gland made to fit the piston rodand wide enough at the top to receive the pressure from the screw capsinner flange 93. To contain the smaller sized piston rod packing I haveproiided a removable split filler piece 92, suit'- ably interlocked whenin -ition.

The lower stuing box cylinder (see Figs. 13 and 42) is a modified formof the stuiiing box 89.. It may carry 45)for the pump the flange 43 thatits intotheupper cavity ofthe water piston 22, said flange forming arecessed interior with passages 46 for the l escape of entrapped waterwhen the pump A is near the end of its upward stroke. 'These passagescommunicate with the annular space 33 and their combined areas can bemodified to suit the speed conditions of the pump.

Inasmuch as the cold water is pumped into the heater at moderatepressures such as 20 to 40 pounds per square inch, while a greater ivolume of hot water must beforced into ytlie boiler at a pressureperhaps of 200 pounds per square inch, I have provided means'forregulating the steam pressure to suit these unequal conditions.- In thetwin or duplex pump unit, it is also desirable to provide 'for theoperation of the pistons so that when one piston is forcing cold waterinto the heater f the other piston will be forcing hot water into theboiler and vice versa. For convenience in construction and operation I`refer to provide a single main steam valve or controlling the admissionof steam to the cylinders, being in turn controlled by supplemental orreversing lvalves operated by the respective pistons Vor piston rods ofthe two pumps. This main valve 95 in valve body 95 cooperates with'ports 96, 97 and^98 and is operated by the rod 101 (see Figs. 7 and 13the pistons 99'and 100 on the opcsite ends of .i

cent faces of the pistons 99 an 100 are suby `135x`

